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Full text of "Contributions to the Metallurgy of Bismuth"

1887.] Contributions to the Metallurgij of Bismuth, 89 



Felruary 10, 1887. 

Professor STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. " Contributions to the Metallurgy of Bismuth." By EDWARD 
Matthey, F.S.A., F.C.S., Assoc. Koy. Sch. Mines. Commu- 
nicated by John Percy, M.D., F.R.S., Pres. Iron and Steel 
Inst. Received August 18, 1886. 

§ 1. Bismuth: its Separation from Gold, and its Refining Action 
upon sams during the Process of Separation. — In bringing the above 
subject under notice, it is necessary to allude to some of the facts dis- 
tinguishing this very interesting metal. 

Bismuth, in some of its important characteristics and reactions, 
resembles lead. And one of the chief points of resemblance between 
these metals is their ready oxidation, and their absorption by bone- 
ashes or wood-ashes whilst so oxydised. I refer of course, to the 
process of cupellation. 

This ancient and serviceable process, still employed universally 
for the separation of gold and silver from lead, is equally applicable 
to bismuth, if associated with these precious metals ; and, like lead, 
bismuth may be readily employed as a vehicle or means of collecting 
gold and silver from their ores in reduction processes ; but its com- 
parative cost accounts for its non- employment in this respect. 

Commercially speaking, bismuth differs from lead in its greater 
value, lead being wori3h at present £1S to £14 per ton,* whilst bismuth 
realises between £700 and £800 per ton ; this high value being due to 
its greater rarity and to its limited and special uses. 

As is well known, bismuth ores are frequently auriferous ; and 
one of the points which it is my desire to bring under notice is the 
effectual separation of the gold from bismuth by a rapid and effica- 
cious process. 

Of course, nothing could be easier than to separate these two 
metals by the ordinary process of cupellation. The gold, by these 

* June, 1886. 



90 Mr. E. Mattliey. [Feb. 10, 

means, is at once rendered ayallable, but wifcli the drawback that not 
only is there a very considerable loss of bismuth by volatilisation 
during the cupellation, but the subsequent recovery of the metal, 
which in the state of oxide has been absorbed by the cupel, is 
rendered necessarj, involving a tedious and troublesome smelting 
operation, the employment of expensive fluxes, and a further con- 
siderable loss of metal. 

Bearing in mind the close resemblance of bismuth to lead in its 
behaviour in the cupellation process, I directed my attention to its 
separation from gold by means of the addition of a small proportion 
of zinc — a method known as the Parkes process, as employed for the 
separation of silver from lead. And this I found successful, the 
natural separation of these two metals during the process of cooling 
proving to be similar in both cases. 

The operation as carried out by me is as follows : — 

The Bismuth holding the gold is melted at the ordinary tempera- 
ture, about two per cent, of melted zinc is then added, and the 
whole brought to a dull red heat. The alloy is then well stirred, 
and the temperature gradually lowered. When at a black heat the 
slight crust formed on the surface is skimmed off and the metal 
again treated with a further quantity of zinc at the higher tempera- 
ture. The whole of the gold will be found in these skimmings, and 
the bismuth v/ill be thus freed from it. 

The skimming^s, consisting of bismuth, gold and zinc, and zine 
oxide, I now treat by a process which quickly renders the gold avail- 
able, and at the same time has the effect of refining the gold from all 
impurities excepting silver during the actual process of extraction. 

This small proportion of bismuth litharge and its charge of gold 
is fused in a clay crucible with a little borax, and allowed to cool 
down in the crucible, or it is poured into a mould with the bismuth, 
litharge, which being perfectly liquid, allows the metallic gold to 
separate by its own gravity, and during its fusion absorbs any base 
metals associated with it as oxides. The bismuth litharge^ in fact, 
acts as a refining agent to the goldj which, when cold, is detached from 
it. This bismuth slag is broken up, re-fused with a little metallic 
bismuth, and is so freed from the last trace of gold which is collected 
by the bismuth, and subsequently extracted. The bismuth litharge 
so freed from gold is then reduced by fusion with carbon to its 
metallic state. 

The quantity of bismuth litharge holding the gold is exceedingly 
small in proportion to the bulk of metal originally treated, as the 
figures hereinafter given will show ; but, by this process the bismuth 
is at once freed from its gold contents with little time, labour, or 
expense. 

I have continuously carried out this method of treatment with the 



1887.] Contributions to the Metallurgy of Bismuth. 91 

most satisfactory results. It will only be necessary to take the figures 
of one operation as an illustration. 

A quantity of 9483 lbs. of bismuth, holding about one per cent, of 
impurity, and 12'5 ounces of gold per ton (equal to 53*5 ounces in 
the bulk), was so treated, and of this nearly 9000 lbs. was imme- 
diately rendered available for commercial use, the skimmingv*?, which 
amounted to 668 lbs. (7*30 per cent, of the bulk), contai^iing the tvJiole 
of the gold. 

These skimmings I oxidised by means of nitric acid, thus obtain- 
ing the greater proportion of the bismuth and what little copper there 
was in solution, from which the bismuth was precipitated by the 
ordinary method, care being taken to saturate the nitric acid by ex- 
tracting the greater portion of the bismuth as nitrate, so as to leave 
a portion of the bismuth as oxide with the gold in order to refine 
it from the impurities existing as oxides when fused with it. This 
residue, collected and dried, was, when dried, fused in clay crucibles, 
with a small quantity of borax, yielding the full amount of gold shown 
by assay. 

A.8 before stated, in these fusions the metallic gold separates from 
the bismuth litharges, and descends to the bottom of the crucible by 
its own gravity. The liquid and supernatant bismuth litharge floats 
upon it and breaks away readily when cold, the gold so obtained being 
associated only with silver, both metals being in fact refined hy the 
action of the bismuth litharge. 

§ 2. Separation of Bismuth from Leac?.— The difficulty surrounding 
the treatment of bismuth associated with other metals by any rapid 
or comprehensive process is well known to the metallurgical chemist. 
I believe I am correct in stating that hitherto the only process 
employed for the refining of bismuth on the Continent — notably in 
Saxony, the chief continental source of this metal — has been that of 
chlorination and subsequent precipitation, a process tedious in itself 
and involving much plant and labour in comparison with the quanti- 
ties of metal operated upon. 

Hapidity of production with a minimum margin of loss, in order 
to free the metal from its impurities and render it marketable as 
quickly as possible, being a great desideratum, induced me to turn 
my attention to its refining by dry processes. In carrying this out I 
have found present most of the metals which are easily seized by and 
become associated with the bismuth itself during the process of reduc- 
tion from its ores,* such as antimony, arsenic, tellurium, lead, copper, 
&c., &c., all of which I have successively and successfully dealt with. 

It is not my intention in this paper to describe the processes 
adopted for the elimination of these several metals, but to confine 

* See Table of Analyses lierewitli. 



92 Mr. E. Matthey. [Feb. 10, 

myself to tlie separation of lead, the presence of wMeh especially 
presented at first great difficulties. 

As stated above, I have found that I can separate one by one the 
metals mentioned above, all of which have been associated with crude 
bismuth which has come under my notice. In this, success though 
gradual, has been complete : but I was still confronted by the fact 
that the lead alloy was retained by the bismuth with a most charac- 
teristic persistency which seemed to defy all efforts of separation 
excepting by tedious wet or acid processes. 

The amount of lead existing in the bismuth I operated upon, after 
freeing it by dry processes from its other impurities, varied from 2 to 
10 per cent. 

Bearing in mind the respective fusing points of lead and bismuth, 
it occurred to me that, as alloys of bismuth and lead fuse at a 
temperature considerably lower than that of bismuth itself, separation 
would possibly take place between the two metals at a certain point 
of cooling ; I therefore made the following experiment : — 

Taking a quantity of bismuth (about 10 cwt.), holding 11*5 per 
cent, of lead, and fusing same, I allowed the metal to cool until the 
major part of it had crystallised, then removing the fluid portion. 

The residue showed by assay only 6*35 per cent, of lead, pointing 
at once to the partial separation I had hoped for. 

These crystals again similarly treated showed only 3*75 per cent, 
of lead. 

The operation repeated gave crystals with only 2 per cent, of lead, 
and a fourth crystallisation brought this down to below 0*5 per cent. 

As a matter of possible interest, I subjoin the progressive results 
during the crystallising operations of several lots up to the point of 
bulking, and of finally separating every trace of lead : — 

Bismuth holding 14*6 per cent. Lead. 

1st crystallisation gave crystals holding 9*8 per cent, of lead. 

2nd 

3rd 

4th 

5th 



Bismuth holding 12 per cent. Lead. 

1st crystallisation gave crystals holding 6*2 per cent, of lead. 

2nd „ „ „ 4*2 

3rd 

4th 



» 


5> 


55 


V X 


55 


55 


5> 


>J 


JJ 


3-8 


»> 


55 


>5 


>» 


5» 


2-5 


55 


J5 


JJ 


5» 


55 


0-4 


»5 


55 



5? 


5» 


55 


-JB M 


5? 


55 


51 


55 


J5 


1-4 


>5 


>t 


l> 


J> 


55 


0-4 


99 


99 



1887.] Contributions to the Metallurgy of Bismuth, 93 



Bismuth holding 7*6 per cent. Lead, 

1st crystallisation gave crystals holding 4*8 per cent, of lead. 

2na ,, ,, ,, o*o ,, ,, 

Qy,A A.Q 

4tli „ „ „ 0-4 „ 



Bismuth holding 11 per cent. Bead. 



1st crystallisation gave crystals holding 5*5 per cent, of lead. 

Jna 5, ,, ,5 Z'o ,, ,, 

•orcl 5, ,, ,, X*U 



>> 5» 



Bismuth holding 5*6 per cewl Bead. 

1st crystallisation gave crystals holding 2*0 per cent, of lead, 
2nd „ „ „ 07 

3rd „ „ under 0*5 



?5 J5 

5? ?> 



Bismuth holding 5*3 per cen^. Bead. 

1st crystallisation gave crystals holding 1*8 per cent, of lead. 

2nd 55 „ ,, 0*6 ,, ,, 

3rd 55 55 under 0*5 „ ,, 



Having attained this point, I worked upon several large quantities 
of metal^ — ^with practically the same results— finally succeeding by a 
continuation of the process in eliminating every trace of lead. 

By the above it will be seen that the process becomes an ex- 
ceedingly simple one, large quantities being treated at one time, 
involving little or no loss, and occupying bours, instead of possibly 
weeks. 

To illustrate the facilities of the separation of lead and bismuth, 
alloys, I give the following figures from metal holding originally 1a.YQ 
per cent, of lead. 

10,675 lbs. produced, in the course of six to seven crystallisations, 
9306 lbs. of available bismuth, the residue 1188 lbs. holding 40 per 
cent, of lead, so that from a quantity of nearly 5 tons of bismutb and 
lead alloy only about half a ton remained, holding practically the 
whole of tbe lead ; the bulk of the bismuth separated by simple crys- 
tallisation holding traces only of lead, which, if necessary, could be 
readily eliminated by further crystallisation. From these facts it is 
apparent that the separation of these two metals can be effected by 
turning to account their relative fusing ^points. 



94 Mi% E. B. Potilton. On a special Colour-lielation [Feb. 10, 

Recapitulation of foregoing Experiment. 

10,675 lbs. leady bismutli, liolding five per cent, lead, yielded 
9306 lbs. of good commercial bismuth bj the crystallization process, 
or within six per cent, of the total contents of pure bismuth. 

Leaving for subsequent treatment — 

Of alloy, holding 40 per cent, of lead, 1188 lbs., which is equal to 
11*13 per cent, of the whole weight of metal treated. 



Average Analysis of the Bismuth 

Bismuth . . . . , 



• ♦ • ♦ 



• • « • • 



« • t » 



» • * • • 



Lead .... 
Antimony . . . 

Arsenic 

Molybdenum . 
Tellurium . . . 

Iron 

Manganese . . . 

Copper 

Tungstic acid. 
.A-iumma . * . * . 
Magnesia . . . 

Carbonic acid. 

Sulphur 

Insoluble earthy matter, cbiefly silica 

Oxygen in combination and loss. . . . . 



• • • • • e « 



* # * • • 



« « • • « 



« « » «r • 



• » • 9 e * * 



• ••••*** 



« « • • • 



res vjorhecl upon, 
... 44-57 

o.qt; 
• •*»••« \J O^t* 

1-26 

5-02 
0-17 
5-25 
0-05 
0-24 
2-45 
0-18 
0-09 
0-81 
1*47 
3-77 
23-12 

o'o/ 

5-19 
100-00 



• •*»**«»» 



« • « « 



• ••«•» 



*e«««iii«« 



II. ** An Inquiry into the Cause and Extent of a special Colonr- 
Eelation between certain exposed Lepidopterons Pupge 
and the Surfaces which immediately surround them." By 
Edward B. Poulton, M.A., of Jesus and Keble Colleges, 
Oxford, Lecturer in Zoology and Comparative Anatomy 
at St. Mary's Hospital, Paddington. Communicated by 
Professor E. Kay Lankester, F.E.S. Received Feb- 
ruary 10, 3887. 

(Abstract.) 

HistoriGa,l,-~-'Mv, T. W. Wood first called attention to the colour- 
relation in pupae (^Entom. Soc. Proc.,' 1867, p. xcix), adducing